Currently, several technologies are known for the processing of crude oil. Of these, thermal cracking is considered to be the most efficient, and it is widely used for converting heavy, higher molecular weight hydrocarbons into lighter, lower molecular weight fractions. The most commonly used cracking technologies are fluid catalytic cracking, delayed coker, and hydrocracking. All of these processes of cracking are associated with certain advantages, as well as significant drawbacks. General advantages include the ability to produce different types of fuel ranging from light aviation kerosene to heavy fuel oils, as well as providing for the separation of hydrocarbon fractions based upon their boiling points.
However, a significant disadvantage of the currently employed methods for synthesizing lighter fuels from crude oil is the high financial cost associated with the realization of the technology. Both capital and operating costs are typically very high for these methods. In particular, the existing technology is realized at high temperatures and pressures of the working medium, and it, therefore, requires specialty materials for the manufacture of chemical reactors, and other specialized equipment. For example, the reactors are typically made from special grade alloy steels. Additionally, for the implementation of hydrocracking technology, it is necessary to use temperatures of up to 600° C. and pressures of up to 150 bars. Still higher temperatures of up to 850° C. are required for the steam cracking processes, where the steam flow rate through the reaction zone may reach the speed of sound. Such special requirements significantly increase capital costs.
Some of the most effective technologies of oil refining use catalyst-based cracking processes. In particular, Fluid Catalytic Cracking (FCC) is one of the most important conversion processes currently used in petroleum refineries because the catalytic cracking produces more gasoline with a higher octane rating. FCC is used to convert the high-boiling, high-molecular weight hydrocarbon fractions of crude oils to more valuable lower molecular weight hydrocarbons in gasoline, diesel fuels, and other products. Modern FCC catalysts are fine powders, and the quality of the FCC process is largely dependent upon the chemical and physical properties of the catalyst. The catalysts used in the reforming processes are typically removed from the reactor, and further require regeneration. Costs associated with the production and/or regeneration of such catalysts constitutes a major portion of operating costs for such processes.
Additionally, the catalysts used in FCC processes are highly sensitive to the content of various impurities in the crude oil. In particular, the presence of sulfur in the crude oil leads to a rapid degradation of the catalytic properties of the catalyst. Thus, it is necessary to pre-treat feedstocks to remove the sulfur (i.e. desulfurization). Moreover, nickel, vanadium, iron, copper, and other contaminants that are present in FCC feedstocks, all have deleterious effects on the catalyst activity and performance. Of these, nickel and vanadium are particularly troublesome. Although hydrodesulfurization of the FCC feedstock removes some of the metals and reduces the sulfur content of the FCC products, it is a very costly option. Further, withdrawing some of the circulating catalyst as spent catalyst, and replacing it with fresh catalyst in order to maintain a desired level of activity for FCC technology, adds to the operational cost of the process.
Plasma chemical methods use various types of electrical discharges to create plasma. Such methods of oil cracking and reforming have been described in various patents and publications. For example, U.S. Patent Publication No. 2005/0121366 discloses a method and apparatus for reforming oil by passing an electrical discharge directly through the liquid. The disadvantage of this method is the low resource electrodes and the associated high probability of failure of ignition sparks between these electrodes. Due to the high electrical resistance of oil, the distance between the electrodes is required to be very small. For example, the distance may be on the order of about 1 mm. However, the inter-electrode distance increases rapidly due to electrode erosion, leading to termination and/or breakdown of the system. Furthermore, the use of such small gaps between the electrodes allows processing of only a very small sample size at any given time.
U.S. Pat. No. 5,626,726 describes a method of oil cracking, which uses a heterogeneous mixture of liquid hydrocarbon materials with different gases, such as the treatment of arc discharge plasma. This method has the same disadvantages associated with the small discharge gap described above, and requires a special apparatus for mixing the gas with the liquid, as well as the resulting heterogeneous suspension. Heating of the mixture by a continuous arc discharge leads to considerable loss of energy, increased soot formation, and low efficiency.
Russian Patent No. 2452763 describes a method in which a spark discharge is carried out in water, and the impact from the discharge is transferred to a heterogeneous mixture of a gas and a liquid hydrocarbon or oil through a membrane. This increases the electrode discharge gap which increases electrode life, but reduces the effectiveness of the impact of the spark discharge on the hydrocarbon or oil. This is because much of the direct contact of the plasma discharge with the hydrocarbon medium is excluded. Additionally, the already complicated construction using a high voltage pulse generator is further complicated by the use of a heterogeneous mixture preparation apparatus and device for separation of the treated medium from the water in which the spark discharge was created.
U.S. Patent Publication No. 2010/0108492, and U.S. Pat. No. 7,931,785 describe methods having a high conversion efficiency of heavy oil to light hydrocarbon fractions. In these methods, the heterogeneous oil-gas medium is exposed to an electron beam and a non-self-maintained electric discharge. However, the practical use of the proposed method is challenging because, in addition to the complicated heterogeneous mixture preparation system, an electron accelerator with a device output electron beam of the accelerator vacuum chamber in a gas-liquid high pressure mixture, is required. The electron accelerator is a complex technical device which significantly increases both capital costs and operating costs. In addition, any use of the fast electron beam is accompanied by a bremsstrahlung X-ray. As such, the entire device requires appropriate biological protections, further adding to the cost.